1. Field of the Invention
The field of invention relates to circuitry for measurement applications with sensors. The invention relates more particularly to sensor interface circuitry for applications using multiple resistance sensors and capacitance sensors.
2. Description of the Related Art
In related art for similar applications are the potentiometer and the Wheatstone bridge. The Wheatstone bridge is by far much more popular than the potentiometer. The Wheatstone bridge has very unique temperature compensation capability with resistance strain gages but has very limited sensitivity. It invariably requires large post-amplification to obtain reasonable measurement sensitivity. Further, a Wheatstone bridge can accommodate measurements from a maximum of only two pairs of sensors. Usually, one of the pairs will have positive changing resistances (like those obtained with tensile strain in resistance strain gages), and the other pair simultaneously uses negative changing resistances (like those obtained with compressive strain). Because of the particular disposition of the positive and negative changing pairs in the Wheatstone bridge, the Wheatstone bridge uniquely provides compensation for sensor resistance changes with ambient temperature. Resistances used for the sensors invariably have tolerances; therefore the Wheatstone bridge always needs initial balancing of the bridge for higher resolution measurements. This balancing is usually accomplished by changing the ratio of the bridge arms.